const sbox = [
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
    0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
    0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
    0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
    0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
    0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
    0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
    0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
    0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
    0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
    0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
    0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
    0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
    0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
    0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
];
const sboxinv = [
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
    0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
    0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
    0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
    0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
    0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
    0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
    0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
    0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
    0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
    0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
    0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
    0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
    0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
    0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
    0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
    0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
    0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
    0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
    0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
    0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
    0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
    0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
    0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
    0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
    0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
    0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
];

function new_context() {
   const ctx = {};
   ctx.key = new Uint8Array(32);
   ctx.enckey = new Uint8Array(32);
   ctx.deckey = new Uint8Array(32);
   return ctx;
}
function rj_xtime(x) {
   const y = (x << 1) & 0xff;
   return (x & 0x80) ? (y ^ 0x1b) : y;
}
function aes_subBytes(buf) {
   let i = 16;
   while (i--) buf[i] = sbox[buf[i]];
}
function aes_subBytes_inv(buf) {
   let i = 16;
   while (i--) buf[i] = sboxinv[buf[i]];
}
function aes_addRoundKey(buf, key, offset) {
   offset = offset || 0;
   let i = 16;
   while (i--) buf[i] ^= key[i+offset];
}
function aes_addRoundKey_cpy(buf, key, cpk) {
   let i = 16;
   while (i--)  buf[i] ^= (cpk[i] = key[i]), cpk[i+16] = key[i+16];
}
function aes_shiftRows(buf) {
   let i, j;
   i = buf[1], buf[1] = buf[5], buf[5] = buf[9], buf[9] = buf[13], buf[13] = i;
   i = buf[10], buf[10] = buf[2], buf[2] = i;
   j = buf[3], buf[3] = buf[15], buf[15] = buf[11], buf[11] = buf[7], buf[7] = j;
   j = buf[14], buf[14] = buf[6], buf[6]  = j;
}
function aes_shiftRows_inv(buf) {
   let i, j;
   i = buf[1], buf[1] = buf[13], buf[13] = buf[9], buf[9] = buf[5], buf[5] = i;
   i = buf[2], buf[2] = buf[10], buf[10] = i;
   j = buf[3], buf[3] = buf[7], buf[7] = buf[11], buf[11] = buf[15], buf[15] = j;
   j = buf[6], buf[6] = buf[14], buf[14] = j;
}
function aes_mixColumns(buf) {
   let i, a, b, c, d, e;
   for (i = 0; i < 16; i += 4) {
      a = buf[i];
      b = buf[i + 1];
      c = buf[i + 2];
      d = buf[i + 3];
      e = a ^ b ^ c ^ d;
      buf[i] ^= e ^ rj_xtime(a ^ b);
      buf[i + 1] ^= e ^ rj_xtime(b ^ c);
      buf[i + 2] ^= e ^ rj_xtime(c ^ d);
      buf[i + 3] ^= e ^ rj_xtime(d ^ a);
   }
}
function aes_mixColumns_inv(buf) {
   let i, a, b, c, d, e, x, y, z;
   for (i = 0; i < 16; i += 4) {
      a = buf[i];
      b = buf[i + 1];
      c = buf[i + 2];
      d = buf[i + 3];
      e = a ^ b ^ c ^ d;
      z = rj_xtime(e);
      x = e ^ rj_xtime(rj_xtime(z ^ a ^ c));
      y = e ^ rj_xtime(rj_xtime(z ^ b ^ d));
      buf[i] ^= x ^ rj_xtime(a ^ b);
      buf[i + 1] ^= y ^ rj_xtime(b ^ c);
      buf[i + 2] ^= x ^ rj_xtime(c ^ d);
      buf[i + 3] ^= y ^ rj_xtime(d ^ a);
   }
}

function aes_expandEncKey(k, rc) {
    let i;
    k[0] ^= sbox[k[29]] ^ (rc[0]);
    k[1] ^= sbox[k[30]];
    k[2] ^= sbox[k[31]];
    k[3] ^= sbox[k[28]];
    rc[0] = rj_xtime(rc[0]);
    for(i = 4; i < 16; i += 4)  k[i] ^= k[i - 4],   k[i + 1] ^= k[i - 3],
                                            k[i + 2] ^= k[i - 2], k[i + 3] ^= k[i - 1];
    k[16] ^= sbox[k[12]];
    k[17] ^= sbox[k[13]];
    k[18] ^= sbox[k[14]];
    k[19] ^= sbox[k[15]];
    for(i = 20; i < 32; i += 4) k[i] ^= k[i - 4],   k[i + 1] ^= k[i - 3],
                                            k[i + 2] ^= k[i - 2], k[i + 3] ^= k[i - 1];
}

function aes_expandDecKey(k, rc)
{
    let i;
    for(i = 28; i > 16; i -= 4) k[i + 0] ^= k[i - 4], k[i + 1] ^= k[i - 3],
                                                k[i + 2] ^= k[i - 2], k[i + 3] ^= k[i - 1];
    k[16] ^= sbox[k[12]];
    k[17] ^= sbox[k[13]];
    k[18] ^= sbox[k[14]];
    k[19] ^= sbox[k[15]];
    for(i = 12; i > 0; i -= 4)  k[i + 0] ^= k[i - 4], k[i + 1] ^= k[i - 3],
                                                k[i + 2] ^= k[i - 2], k[i + 3] ^= k[i - 1];
    rc[0] = (rc[0]>>1) ^ ((rc[0] & 1) ? 0x8d : 0);
    k[0] ^= sbox[k[29]] ^ (rc[0]);
    k[1] ^= sbox[k[30]];
    k[2] ^= sbox[k[31]];
    k[3] ^= sbox[k[28]];
}
function aes256_init(ctx, k) {
    let rcon = new Uint8Array([1]), i;
    for (i = 0; i < ctx.key.length; i++) ctx.enckey[i] = ctx.deckey[i] = k[i];
    for (i = 8; --i;) aes_expandEncKey(ctx.deckey, rcon);
}
function aes256_done(ctx) {
    let i;
    for (i = 0; i < ctx.key.length; i++)
        ctx.key[i] = ctx.enckey[i] = ctx.deckey[i] = 0;
}
function aes256_encrypt_ecb(ctx, buf) {
    let i, rcon;
    aes_addRoundKey_cpy(buf, ctx.enckey, ctx.key);
    for(i = 1, rcon = new Uint8Array([1]); i < 14; ++i) {
        aes_subBytes(buf);
        aes_shiftRows(buf);
        aes_mixColumns(buf);
        if( i & 1 ) aes_addRoundKey(buf, ctx.key, 16);
        else aes_expandEncKey(ctx.key, rcon), aes_addRoundKey(buf, ctx.key, 0);
    }
    aes_subBytes(buf);
    aes_shiftRows(buf);
    aes_expandEncKey(ctx.key, rcon);
    aes_addRoundKey(buf, ctx.key, 0);
}

function aes256_decrypt_ecb(ctx, buf) {
    let i, rcon;
    aes_addRoundKey_cpy(buf, ctx.deckey, ctx.key);
    aes_shiftRows_inv(buf);
    aes_subBytes_inv(buf);
    for (i = 14, rcon = Uint8Array([0x80]); --i;) {
        if( ( i & 1 ) ) {
            aes_expandDecKey(ctx.key, rcon);
            aes_addRoundKey(buf, ctx.key, 16);
        } else aes_addRoundKey(buf, ctx.key, 0);
        aes_mixColumns_inv(buf);
        aes_shiftRows_inv(buf);
        aes_subBytes_inv(buf);
    }
    aes_addRoundKey( buf, ctx.key, 0);
}

module.exports = {
   aes256_init,
   aes256_done,
   aes256_encrypt_ecb,
   aes256_decrypt_ecb,
   new_context,
};
